False Killer 405

dorsal fi n located at the midpoint of the back, and distinctive fl ip- pers (with a bulge on the leading edge). Scars from inter- and intra- specifi c interactions eventually are re-pigmented, unlike in the closely related Risso’s . False killer are slightly sexually dimorphic, with the of males protruding farther forward than in females. Their teeth are large and conical, with 7–11 in each of the upper jaws and 8–12 in each lower jaw.

F II. Distribution and Abundance False killer whales are found in all tropical and warm temperate oceans of the world, and occasional records of their presence in cold temperate waters have also been documented. Although they are typically characterized as pelagic in habits, they do approach close to shore and utilize shallow waters around oceanic islands. These oce- False anic habits have hindered the study of this species in the wild, and crassidens most of what is known comes from stranded individuals, captive ani- F mals, and limited observations of groups around oceanic islands. In ROBIN W. BAIRD the Pacifi c there is evidence of limited gene fl ow, and the population around the main Hawaiian Islands is demographically isolated from I. Characteristics and the rest of the tropical Pacifi c (Chivers et al., 2007). No estimates of worldwide population size are available, although false killer whales he is one of the larger members of the fam- appear to be naturally uncommon throughout their range. Regional ily Delphinidae, with adult males reaching lengths of almost estimates for the Hawaiian Islands Exclusive Economic Zone T6 m and females reaching up to 5 m. The common name comes suggest a small population size, in the low hundreds of individuals. from similarity not in external appearance to the killer whale ( No information on population trends is available. orca ) but rather in skull morphology of these two species. In fact, the two species do not appear to be closely related; based on genetic simi- larity, false killer whales appear to be most closely related to the Risso’s III. Ecology dolphin ( Grampus griseus), melon-headed whale ( Peponocephala electra), ( Feresa attenuata), and pilot whales False killer whales are one of the handful of species that regularly (Globicephala spp.). There is evidence of geographic variation in skull mass strand, with the largest stranding recorded of 835 individuals. morphology (Kitchener et al., 1990), but no are currently The diet appears to be diverse, in terms of both species and size of recognized. prey (Fig. 2). In general they feed on a variety of oceanic squid and Largely black or dark gray in color (usually with a lighter blaze fi sh but have also been documented feeding on smaller delphinids on the ventral surface between the fl ippers), it is easily recogni- being released from purse-seines in the eastern tropical Pacifi c. zable with its rounded head, gracile shape (Fig. 1) , small falcate One case of predation on a ( Megaptera novaean- gliae) calf has also been recorded, and they have been documented attacking sperm whales (Physeter macrocephalus ). Nonaggressive

Figure 1 The highly acrobatic false killer whale (Pseudorca crassi- dens) leaping while chasing prey. The false killer whale does not resemble the killer whale (Orcinus orca) in external appearance, Figure 2 A false killer whale attacking a mahi-mahi (Coryphaena although the skulls of the two species are quite similar. Photograph hippurus). Prey sharing in the wild and in captivity is frequently © Robin W. Baird. observed for this species. Photograph © Daniel J. McSweeney. 406 Feeding Morphology

interspecifi c associations with bottlenose ( Tursiops trunca- Baird, R.W. et al. (10 authors). (2008). False Killer Whales (Pseudorca tus) and rough-toothed dolphins ( Steno bredanensis) have also been crassidens) around the main Hawaiian Islands: long-term site sidelity, reported. No predators of false killer whales have been reported, inter-island movements, and association patterns. Mar. Mamm. Sci. although large sharks and killer whales likely take some individuals. 24, 591–612. Brown , D. H. , Caldwell , D. K. , and Caldwell , M. C. ( 1966 ). Observations on the behavior of wild and captive false killer whales, with notes on IV. Behavior and Physiology associated behavior of other genera of captive delphinids. Los Angeles False killer whales are considered to be extremely social, usually County Mus. Contrib. Sci. 95 , 1 – 3 2 . traveling in groups of 20 to 100 individuals. Long-term (15 years) Chivers , S. J. , Baird , R. W. , McSweeney , D. J. , Webster , D. L. , associations among individuals have been documented in Hawaiian Hedrick , N. M. , and Salinas , J. C. ( 2007 ). Genetic variation and evi- waters, and analyses of associations of photo-identifi ed individuals dence for population structure in eastern North Pacifi c false killer indicate strong bonds among individuals (Baird et al., 2008). Such whales (Pseudorca crassidens ) . Can. J. Zool. 85 , 783–794 . Kasuya , T. ( 1986 ). False killer whales . In “ Report of Investigation in bonds are also evident from their propensity to strand en masse, and Search of Solution for Dolphin- Confl ict in the Iki Island by the affi liative behavior of stranded . False killer whales are Areas ” ( T. Tamura , S. Ohsumi , and S. Arai , eds ) . active during the day, and food sharing in the wild has been regularly Agency , Tokyo. recorded. Little is known about the diving behavior of this species; Kitchener , D. J. , Ross , G. J. B. , and Caputi , N. ( 1990 ). Variation in skull one tagged dove for up to 12 min and to depths of over 230 m. and external morphology in the false killer whale, Pseudorca crassi- F dens, from Australia, Scotland and . Mammalia 54 , V. Life History 119 – 134 . Koen Alonso , M. , Pedraza , S. N. , Schiavini , A. C. M. , Goodall , R. N. P. , Life history information comes entirely from stranded individu- and Crespo , E. A. ( 1999 ). Stomach contents of false killer whales als. Because the deposition rate of growth layer groups in the teeth (Pseudorca crassidens ) stranded on the coasts of the Strait of has not been calibrated, there is some uncertainty in life history Magellan, Tierra del Fuego. Mar. Mamm. Sci. 15 , 712 – 724 . parameters. Both sexes are thought to mature between about 8 and Odell , D. K. , and McClune , K. M. ( 1999 ). False killer whale Pseudorca 14 years of age, although there is some suggestion that males may crassidens (Owen, 1846) . In “ Handbook of Marine ” mature later. Maximum longevity has been estimated at 57 years for ( S. Ridgway, ed. ) , Vol. 6 , pp. 213 – 243 . Academic Press , New York . males and 62 years for females (Kasuya, 1986 ). Calving interval for Palacios , D. M. , and Mate , B. R. ( 1996 ). Attack by false killer whales one population has been reported as almost 7 years, and calving may (Pseudorca crassidens ) on sperm whales (Physeter macrocephalus ) in occur year-round, with a peak in late winter. the Galapagos Islands. Mar. Mamm. Sci. 12 , 582 – 587 . Purves , P. E. , and Pilleri , G. ( 1978 ). The functional anatomy and general biology of Pseudorca crassidens (Owen) with a review of hydrody- VI. Interactions with Humans namics and acoustics in . Invest. Cetacea 9 , 67 – 227 . A number of types of interactions between humans and false Stacey, P. J. , and Baird , R. W. ( 1991 ). Status of the false killer killer whales have been documented. In Hawaii they are regularly whale , Pseudorca crassidens , in Canada. Can. Field-Nat. 105 , encountered by commercial whale- or dolphin-watching vessels 2nd 189 – 197 . often bowride. They have been maintained in captivity in a number Stacey, P. J. , Leatherwood , S. , and Baird , R. W. ( 1994 ). Pseudorca crassi- dens . Mamm. Sp. 456 , 1 – 6 . of aquaria around the world, including in Japan, the United States, the Netherlands, Hong Kong, and Australia. They have been suc- cessfully bred in captivity in several locations, and there they have produced viable interspecies hybrids with bottlenose dolphins. False killer whales are one of several species of odontocetes that occasion- ally steal fi sh from both commercial and recreational fi shermen, with these types of interactions noted in Japan, Hawaii, the , and the Gulf of Mexico. Feeding Morphology Confl icts with fi sheries have resulted in direct killing in Japan. Small numbers have been occasionally taken in fi sheries, both directly CHRISTOPHER D. MARSHALL and incidentally as . In Hawaiian waters the number killed or seriously injured incidentally in the longline fi shery is greater than the population is thought to be able to sustain. They are one of a growing I. Functional Morphology list of species that has been recorded ingesting discarded plastic, and unctional morphology is a diverse fi eld of biology that inte- high levels of toxins have been documented in tissues collected from grates anatomy, biomechanics, and behavior. It is the study of stranded animals. It is unknown, however, whether such toxins con- Fstructure, its relationship to function, and organismal adapta- tribute to immunosuppression in this species. tion. Marine mammals, and their adaptations to the aquatic envi- ronment, have interested functional morphologists for long time. See Also the Following Articles Accordingly, our knowledge of the anatomy of marine mammals is extensive for many species, and new data continues to compile quickly.

Delphinids ■ Indo-West Pacifi c Marine Mammals However, direct experimental investigations are largely lacking relative to terrestrial mammals. This has been due to the diffi culty of working References with large mammals in an aquatic environment, and the lack of tech- Acevedo-Gutierrez , A. , Brennan , B. , Rodriguez , P. , and Thomas , M. nology that can be taken in the fi eld. As a result morphology has been ( 1997 ). Resightings and behavior of false killer whales (Pseudorca used extensively to predict function and behavior of marine mammals. crassidens ) in Costa Rica. Mar. Mamm. Sci. 13 , 307 – 314 . However, experimental work regarding functional and behavioral